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Re: [patch] Improve loop array prefetch for IA-64
- From: "Steven Bosscher" <stevenb dot gcc at gmail dot com>
- To: "Canqun Yang" <canqun at yahoo dot com dot cn>
- Cc: gcc at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org
- Date: Fri, 2 Jun 2006 11:50:18 +0200
- Subject: Re: [patch] Improve loop array prefetch for IA-64
- References: <firstname.lastname@example.org>
On 6/2/06, Canqun Yang <email@example.com> wrote:
This patch results a performance increase of 4% for SPECfp2000 and 13% for NAS benchmark suite on
Itanium-2 system, respectively. More performance increase is hopeful by further tuning the
parameters and improving the prefetch algorithm at tree level.
--- ia64.h (revision 114307)
+++ ia64.h (working copy)
@@ -1985,13 +1985,18 @@
??? This number is bogus and needs to be replaced before the value is
actually used in optimizations. */
-#define SIMULTANEOUS_PREFETCHES 6
+#define SIMULTANEOUS_PREFETCHES 18
Is the number still bogus as the comment suggests, or is there a
rationale for 18? It looks quite high.
+/* A number that should roughly corresponding to the nunmber of instructions
+ executed before the prefetch is completed. */
+#define PREFETCH_LATENCY 400
Likewise. Is 400 cycles the memory latency on itanium-2?